The aim of this study is to examine how different sowing times affect the germination dynamics of maize hybrids with different ripening periods, as well as their impact on maize development and yield. The experiment was conducted in Hungary, at the Látókép Experimental Station of the University of Debrecen, on calcareous chernozem soil, in a growing season with average precipitation (2023). In the field experiment, three sowing dates were used: Sowing Date I (April 17), Sowing time II (April 24), and Sowing time III (May 23). The same hybrids were included in the experiment for all three sowing dates (H1: FAO 380, H2: FAO 490). Following the germination dynamics test, plant height and relative chlorophyll content (SPAD value) were measured in the stand at three time points: 6-leaf (V6), 12-leaf (V12), and 50% silking (R1) phenological phases. During the first two days of the germination phase, both early and medium-ripening hybrids germinated at nearly the same percentage (H1: 76%, H2: 75%) in Sowing Date I, while in Sowing Date II (H1: 84%, H2: 88%) and Sowing Date III (H1: 87%, H2: 84%), the difference in the germination dynamics of the hybrids was more significant. Between phenophases V6 and R1, the percentage increase in relative chlorophyll content (SPAD value) was highest for hybrid H1 in Sowing Date I and for hybrid H2 in Sowing Date II, while it was lowest for both hybrids in Sowing Date III. The influence of sowing dates on SPAD values was detectable in the V12 phenophase (Sowing Date II p<0.005) for the H1 hybrid and in the V6 (Sowing time III, p<0.005) and V12 phenophase (Sowing time II, p<0.005). Based on the height data measured in different phenological phases, sowing date influenced the growth of maize hybrids, but this effect was not statistically significant in all cases (R1). For the different maize hybrids, the differences in yield results between the hybrids within the examined sowing dates and within each sowing date were not statistically significant. This suggests that sowing date did not have a pronounced effect on the yield of any of the hybrids. At the same time, however, the best sowing date (H1-Sowing date I. 14.959 t/ha; H2-Sowing date II. 14.208 t/ha) may allow for better water and nutrient utilisation and avoid heat stress or drought periods affecting flowering.
The statistically significant strongest correlations between SPAD value and yield for both maize hybrids were found at Sowing Date I and Sowing Date III in the R1 phenological phase (H1 – Sowing Date I: r=0.990**, Sowing Date III: r=0.999***; H2 – Sowing Date I: r=0.976*, Sowing Date III: r=0.944*).